A conventional screw 1 for quickly penetrating through hard object is disclosed in FIG. 1, and generally includes a head 11, a shank 12 extending therefrom, a plurality of threads 13 spirally formed on the shank 12 along the shank's axial line, and an end section 14 extending outwardly from the shank 12. The end section 14 has a drilling portion 141 formed on the shank 12, a conically-shaped tip portion 142 adjacent to the drilling portion 141 and a plurality of grooves 143 formed in the drilling portion 141 and the conically-shaped tip portion 142. Moreover, each groove 143 forms respective cuffing edges 144.
Some shortcomings are found when using the convention screw and described as follows:
1. The cone-shaped tip portion 142 lacks guiding device so that the screw 1 has to be maintained to be perpendicular to the object 2 or the screw 1 could slip away so that the user has to exert a large force to penetrate the cone-shaped tip portion 142 into the object 2 at the first stage of screwing the screw 1 into the object 2.
2. After the cone-shaped tip portion 142 is merged into the object 2, the cutting edges 144 cut the fibers of the object 2 and debris quickly fills the grooves 143. The resistance from the object 2 is increased because that the grooves 143 are filled with the debris and the debris expands laterally and a huge stress is applied to the cutting edges 144. This makes the penetration to be difficult and the cutting edges 144 could be broken.
3. Continuing the afore reasons, the accumulated debris of the object 2 might expand to crack the object 2 if the debris is not well guided away from the object 2.
4. The grooves 143 are defined only on the drilling portion 141 and the conically-shaped tip portion 142, so the fastening function therefore decreases.
Therefore the present invention provides a screw which is able to enhance the screwing speed, securing effect of the screw and labor-saving effects thereof.